1. Field of the Invention
The present invention relates to a ceramic shaped body-positioning system, which is used for accurately conveying the ceramic shaped bodies to the following step by adjusting positions of the ceramic shaped bodies.
2. Description of the Related Art
Heretofore, the following process is known as an example of a process for producing ceramic products such as ceramic honeycomb structural bodies. First, ceramic shaped bodies are obtained by molding a ceramic material and cut in a given length. Then, the cut ceramic shaped bodies are individually placed on cradles, and the cradles on which the ceramic shaped bodies are placed are moved on and along a conveyor path. After the movement, the ceramic shaped bodies are then dried in such a state that a given number of (for example, five) ceramic shaped bodies are aligned, and both end face positions of the dried ceramic shaped bodies are cut for finish working. Finally, the finish worked ceramic shaped bodies are fired to obtain ceramic products.
In the aforementioned conventional process for producing the ceramic honeycomb structural bodies, when, for example, the ceramic shaped body is conveyed to a finishing step after drying, it is necessary to position the ceramic shaped body by correcting lateral and directional deviations of the ceramic shaped body on a table on which the ceramic shaped body is placed in order to accurately convey the ceramic shaped body to the subsequent finishing step. NGK Insulator, Ltd. discloses a technique for the above positioning in JP-A-61-226415, in which a plurality of actuators driven by air cylinders center the shaped bodies to a predetermined position on a conveyor belt in a simple and precise manner.
In the aforementioned conventional positioning system for the ceramic shaped bodies, when a green ceramic honeycomb shaped body is to be positioned, a shock is applied to the ceramic honeycomb shaped body through contacting the actuator upon a peripheral face of the ceramic honeycomb shaped body. Even if such a shock acts upon the ceramic honeycomb shaped bodies, the conventional ceramic honeycomb shaped bodies are not deformed, cracked or broken since such ceramic honeycomb shaped bodies have a cell-wall thickness of about 150 xcexcm and a cell density of about 400 cell/sq. in. and thus have high strengths. Therefore, final ceramic products can be obtained without any problems.
However, thin-walled ceramic honeycomb shaped bodies having a cell-wall thickness of 120 xcexcm or less and a cell density of about 400-1600 cell/sq. in., which are highly demanded these days, are much weaker than the conventional shaped bodies especially in the green state. Thus, when the thin-walled ceramic honeycomb shaped bodies are positioned with a conventional positioning system for the ceramic shaped bodies, the ceramic shaped body may be deformed, cracked or, in an extreme case, even broken with the shock caused by the actuators since it is difficult to reduce the speeds of the actuators at the time of gripping the ceramic honeycomb shaped body. On the contrary, if such a ceramic honeycomb shaped body is chucked with a weak force so as not to break it, another problem of a poor positioning accuracy occurs. The problem is more significant especially when the ceramic honeycomb shaped body having an odd-shaped (asymmetric) cross section is to be positioned.
It is a conventional practice for overcoming the above problems that lengths of arms and gripping rollers are adjusted or replaced according to the kinds of products to modify a chucking unit. Especially for odd-shaped products, specially designed arms and rollers are required. However, such an adjustment or a replacement is time-consuming and causes a low productivity.
It is, therefore, an object of the present invention to solve the above problems and to provide a ceramic shaped body-positioning system which can accurately position even thin-walled ceramic shaped bodies without causing deformations, cracks or breakages.
The ceramic shaped body-positioning system according to the present invention is used for positioning the ceramic shaped body to accurately convey the ceramic shaped body to a next step, which comprises a centering table for placing the ceramic shaped body, a plurality of chucking units comprising a chucking body and a ceramic shaped body-pushing member provided in the chucking body, and a drive unit for moving the chucking units toward/away from the ceramic shaped body on the centering table, wherein the drive unit makes the plurality of chucking units simultaneously approach and push the ceramic shaped body on the centering table while controlling positions and speeds of the chucking units, thereby adjusting the positions of the ceramic shaped body on the centering table with giving substantially no destructive shock on the ceramic shaped body.
In the aforementioned positioning system according to the present invention, the plurality of chucking unit simultaneously approach and push the ceramic shaped body to adjust the position of the ceramic shaped body on the centering table while controlling the positions and the speeds of the chucking units, therefore even if the positioning system is applied for the ceramic shaped bodies having low strength such as thin-walled ceramic honeycomb structural bodies, the ceramic shaped body can be accurately positioned without causing deformations, cracks and breakages.
In a preferred embodiment of the present invention, it is preferable that the drive unit for moving the chucking unit comprises at least one servomotor, since the system can control the positions and the speeds of the chucking unit more accurately than the conventional system driven by air cylinders does. It is also preferable that the ceramic shaped body-pushing member is configured in a manner that it can be detachably mounted at any of given positions on the chucking body, since the system can be adapted to position ceramic shaped bodies having different shapes. Moreover, in this case, it is preferable that the chucking body is provided with a plurality of holes, a shaft are provided for the ceramic shaped body-pushing member, and the shaft is inserted into any of the hole to selectively set the ceramic shaped body-pushing member in the chucking body, since the ceramic shaped body-pushing member can be easily and detachably mounted at a given position on the chucking body. Furthermore, when the chucking body has a planar form and a plurality of holes are provided in the chucking body in a line, the present invention can be more suitably applied for, for example, the cylindrical ceramic shaped bodies having different diameters. When the chucking body has a L-shaped planar form and a plurality of holes are provided and aligned in the chucking body in a L-shape, the present invention can be applied for the odd-shaped ceramic shaped bodies having asymmetric, for example, pentagonal cross sections. Either of the above is preferable.